1. Field of the Invention
The present invention provides a resist spray nozzle resetting device, namely a device for achieving uniformity of resist coating on a semiconductor wafer.
2. Description of the Prior Art
In semiconductor manufacturing processes, a semiconductor wafer must go through many coating processes from start to finish, such as lithographic resist and developer coating processes. With the narrowing line width in semiconductor processes, photolithographic technology has become critical, for it is with photolithography that all the MOS components, metallic wires, thin film patterns and dopant regions are made. Moreover, the pattern-transferring process, mandatory in photolithography, is complicated and subtle, and so only a precise pattern of resist can ensure the reliability of later processes.
In today""s market, most resist coating processes are performed by spin-coating liquid resist over a wafer to form a resist layer with an even thickness. This forms a light-sensitive photo-emulsion layer. Since the uniformity of the thickness of a resist layer can later affect the resolution, the depth of focus (DOF), and even the quality of the wafer, it is important in wafer production to know how to achieve and maintain the uniformity of the resist layer.
Please refer to FIG. 1. FIG. 1 is a front view of a resist coating device 10 according to the prior art. As shown here, the resist coating device 10 comprises a rotary robotic arm 12 and a spray nozzle 14. The spray nozzle 14 has a covering nut 16 fastened on the rotary arm 12. The spray nozzle 14 sprays resist 18 over a wafer""s surface 20 which, positioned on a vacuum rotary station 22, is kept in rotating motion. Ideally, the spray nozzle aims straight at the midpoint 26 of the wafer 20; in other words, it forms a line with the central axis 24, so that the resist 18 drops directly on the midpoint 26 of the wafer 20 and coats the wafer surface. Unfortunately, sometimes the spray nozzle 14 might move astray from the center axis 24 due to maintenance errors or operating negligence, causing the resist 18 to fall off the midpoint 26, resulting in a non-uniform resist coating. Even though resetting of the spray nozzle 14 can be done manually, if it is off of the central axis 24, it wastes both time and money, and alignment errors after manual resetting are not negligible.
The purpose of the present invention is to provide a spray nozzle resetting device to correct the weaknesses of the conventional counterpart described above.
Another purpose of the present invention is to provide a spray nozzle resetting device to avoid misalignment problems, so as to improve the uniformity of the resist layer.
In a preferred embodiment of the present invention, a spray nozzle resetting device comprises a spray nozzle for spraying resist on the midpoint of a wafer, a rotary robotic arm, a resist-delivering duct connected to one end of the spray nozzle, a covering nut, a resetting ring, a fixing ring connecting the covering nut to the rotary robotic arm, and a spring positioned between the covering nut and the resetting ring. The covering nut has an opening of diameter D. The resetting ring has a rotary part with a diameter equal to or less than D, and at last two protrusions. The rotary part fits in the opening of the covering nut. The fixing ring is used to fix the covering nut to the rotary robotic arm, and it has two recesses corresponding to the two protrusions to interact with the two protrusions.
In the preferred embodiment, the midpoint of the resetting ring is not aligned with the two protrusions. To move the spray nozzle, the operator can lift up the rotary part of the fixing ring and rotate it to a desired angle, with the spray nozzle rotating along with it. For performing the resist coating process, the operator can rotate the rotary part in the reverse direction until the two protrusions re-catch on the two recesses, so as to again aim the spray nozzle at the midpoint of the wafer.